Agriculture equipment such as a combine or agricultural vehicle utilizes a head or other implement to perform various operations on a field. Combines often employ an implement such as a harvester or header attached to a feeder to harvest a crop or other plant-related matter. The feeder receives the cut or harvested crop from the header and provides the harvested crop to various pieces of equipment within the combine which perform assorted operations on the harvested crop such as sorting, separating, spreading, storing, or other agricultural functions.
Generally, combines have a combustion engine or mechanical power source indirectly driving the various pieces of equipment which operate on the harvested crop. The various pieces of equipment can include, but are not limited to, a feeder which receives the harvested crop from the header and transports the harvested crop to within the combine, a rotor which receives the harvested crop from the feeder and spins axially to thresh or separate the seed from the non-seed material of the harvested crop, a shoe shaker which separates additional seed from the non-seed material from the rotor, a straw spreader which spins to throw the non-seed material received from the shoe shaker out of the combine, a tailings elevator which conveys seed from the shoe shaker to the rotor, a clean grain elevator which transports seed from the rotor to the grain storage tank or external grain storage area, a discharge beater, a chopper which cuts the non-seed material for spreading by the straw spreader, a cleaning fan which provides cross air movement across the seed material for cleaner seed material as it is conveyed through the combine, a rotary air screen fan which provides cooling for the combustion engine, as well as other types of devices which are driven by the engine. These pieces of equipment (e.g., the rotor) are often indirectly driven via a chain, axle, gear mechanism, or belt such as a rotor-drive belt.
As the load increases on the piece of equipment such as the rotor, the engine speed and rotor speed both decrease proportionally. If the load is great enough, the load overcomes the forces between the rotor-drive belt and the engine or between the rotor-drive belt and the rotor and causes the rotor-drive belt to slip. Sustained loads at these high levels can make the belt slip even more, thereby resulting in no torque being transferred from the engine to the rotor and consequently causing a plugged or jammed rotor. When the rotor plugs, the harvested crop cannot be transported or operated on by the rotor and the combine fails to efficiently harvest the crop.
Generally, it is useful to provide the operator with indicia of whether the coupling mechanism or belt which is indirectly driving the various pieces of equipment such as the rotor is slipping so the operator can take appropriate action to avoid a plug condition. For example, when the rotor-drive belt begins to slip, the operator can reduce the ground speed of the combine, thereby alleviating the load on the rotor. If the operator is able to reduce ground speed before the plug condition exists, the load on the rotor is decreased and the rotor can successfully operate on the harvested crop within it.
Heretofore, combines have included slip alarms which provide an audible or visual warning of a slip condition. These prior art slip alarms monitor rotor speed to determine whether the rotor drive belt is potentially slipping. In these prior art systems, the slip warning was provided when the rotor speed fell below a threshold which represented a percentage of the unloaded rotor speed. However, relying solely on one speed parameter such as the rotor speed to determine a slip condition is inaccurate and more particularly relying solely on a rotor speed parameter is imprecise especially as the belt wears. As the belt wears, the rotor-drive belt tends to slip at a higher rotor speed. Thus, these prior art slip alarms cannot alert the operator in an appropriate amount of time if the belt is worn because they are not able to compensate for belt wear. Accordingly, there is a need for a more accurate slip monitoring system. Further, there is a need for a slip warning system which can adequately warn of slip conditions over the operating life of a belt in a combine.